Slip joints are designed to allow exhaust system parts to move with respect to one another. Such movement may be due to thermal expansion and/or movement from different parts of the vehicle. The joint permits movement between the exhaust system parts so that they are not damaged and the parts they are connected to, such as the engine, is not damaged. This permitted movement is especially important in heavy duty diesel engines due to the increased length of the exhaust manifold.
There are varying known techniques used to allow the joints to move. One method connects one part with another without a specific sealing component. Of course, this method permits emissions to escape between the two parts. It is expected that this method will no longer be permitted or available in the future with increased restrictions on emissions. Additionally, particulates in the emissions become stuck between the components. The particulates stick together then stick the parts together. Once the parts are stuck together they are not able to move with respect to one another, as they should. Once the parts are stuck together it makes them impossible to service. This method can also be disadvantageous because it can require welding operations and/or large amounts of force to connect the parts.
Another known method utilizes split rings between two parts. However, the rings are expensive, precision parts that require special hardware machining. Further, they only result in average sealing performance between the parts. Additionally, the quality that provides them some sealing capability also increases friction between the mated parts, thus impeding the sliding function of the joint.
Another method comprises the use of bellows. Bellows may provide a good seal, but the material can be expensive and its installation is inconvenient. At the least they are known to be bulky and heavy. Further, there are concerns about the durability of the bellows material. Lastly, bellows only seal against the escape of hot gases after the gases have traveled through the joint itself. This exposes the joint to high temperatures that can damage hardware and permit exhaust particulates an opportunity to become stuck in the joint. Particulates that become stuck in the joint may impede the function of the joint, and prevent movement of the parts with respect to one another as discussed above.
In view of the disadvantages of the known sealing means, it would be advantageous to provide a means to prevent exhaust gases from escaping between two parts and to permit the two parts to slip with respect to one another to at least accommodate thermal expansion. Further, it would be advantageous to provide a joint that requires less hardware preparation, that is easy to install, including installation by hand, that is lightweight, does not take up much space and is easy to maintain or replace.